1. Field of the Invention
The invention relates to identification of etiology of autism.
2. Description of the Related Art
Autism is a developmental disorder, which manifests itself during early childhood. In the autistic child, communications and social interactions, are severely impaired. Unable to learn from the natural environment as most children do, the child with autism generally shows little interest in the world or people around him. Although some children with autism develop normally and even acquire advanced skills, most exhibit a wide range of behavioral problems. In reality, autism affects the way a person comprehends, communicates and relates to others. Autism was originally thought to be primarily a psychiatric condition. However, further investigation showed that genetic and environmental factors are implicated in the pathogenesis of autism (1-8). The effects of environmental factors such as infections and toxic chemicals on gene expression result in biochemical, immunological and neurological disorders found in children with autism.
Diagnosis of Autism
Because we have no definitive diagnostic tests for the biological manifestations of autism, it remains one of the only neurological disorders that must be diagnosed almost entirely through behavioral symptoms. We know that autism interferes with the normal development of the brain in the areas of reasoning, social interaction, communication skills and emotions such as love and empathy. Children and adults with autism typically have deficiencies in verbal and nonverbal communication, social interactions, and leisure or play activities. Autistic people may exhibit repeated body movements such as hand flapping, rocking, or spinning; they may have unusual responses to people or attachments to objects; and they may resist changes in routines. In some cases they may exhibit aggressive or self-injurious behavior.
According to the DSM-IV or Diagnosis and Statistical Manual for Mental Disorders, 4t′ edition, published by the American Psychiatric Association (9), autism is classified as a Pervasive Developmental Disorder (PDD) characterized by twelve diagnostic criteria. These criteria fall into three categories—impairments in social interaction, impairments in communication, and a restricted repertoire of activities and interests. A diagnosis of autism requires that a child display at least six of these twelve symptoms, with a minimum number in each category.
DSM IV Diagnostic Criteria for Autism
Diagnosis Criteria for 299.00 Autistic Disorder
A. A total of six (or more) items from (1), (2), and (3), with at least two from (1), and one each from (2) and (3):    1. qualitative impairment in social interaction, as manifested by at least two of the following:            a. marked impairment in the use of multiple nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction        b. failure to develop peer relationships appropriate to developmental level        c. lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g., by a lack of showing, bringing, or pointing out objects of interest)        d. lack of social or emotional reciprocity            2. qualitative impairments in communication as manifested by at least one of the following:            a. delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)        b. in individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others        c. stereotyped and repetitive use of language or idiosyncratic language        d. lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level            3. restricted repetitive and stereotyped patterns of behavior, interests and activities, as manifested by at least one of the following:            a. encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus        b. apparently inflexible adherence to specific, nonfunctional routines or rituals        c. stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)        d. persistent preoccupation with parts of objects        
B. Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years: (1) social interaction, (2) language as used in social communication, or (3) symbolic or imaginative play.
C. The disturbance is not better accounted for by Rett's Disorder or Childhood Disintegrative Disorder.
If a child does not fit the definition of autism given above, he or she may be diagnosed with a condition called Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS). Such a diagnosis of non-specific forms of Pervasive Developmental Disorder (PDD) may include atypical types of autism that do not fall into the above categories because of late age of onset, for example, or subthreshold or atypical symptoms. According to the DSM-IV, this diagnosis is to be used when autistic-like behaviors are present—in particular, when there is severe impairment in the development of social and verbal communication skills—but the child does not meet the criteria for classic autism or any other specific Pervasive Developmental Disorder, Schizophrenia, Schizotypal Personality Disorder or Avoidant Personality Disorder (9).